Comparison of Various Thin-Film-Based Absorber Materials: A Viable Approach for Next-Generation Solar Cells

Round 1

Reviewer 1 Report

Mamta et al. demonstrate a simulation work on various thin film absorber materials based on CdS. The following points should be addressed:

1. Please write down the major mathematical equations used to calculate the overall conversion efficiencies of the solar cell.
2. most importantly, there is lack of mechanistic discussion on the effects. For example, please provide more mechanistic view to discuss why “As the electron affinity value increases, the efficiency gets decreased for all the four different absorber layers”rather than only reporting the results. The same applies to other parameters where sufficient mechanistic view is not provided.
3. Figure 7: please provide the detailed calculation method to obtain the energy levels of Ec and Ev. How do they compare with those reported in the literature obtained via DFT or XPS/PES?

Author Response

 Here, I am attaching the pointwise responses to the referee’s comments.

REFEREE REPORT(S)

Reviewer # 1

Comment 1: Please write down the major mathematical equations used to calculate the overall conversion efficiencies of the solar cell

The Response: Authors are thankful to the reviewer for their valuable comment. In the revised manuscript, the major mathematical equations (Poisson and continuity, open-circuit voltage, fill factor, and efficiency) have been stated as said above.

Comment 2: Most importantly, there is lack of mechanistic discussion on the effects. For example, please provide more mechanistic view to discuss why “As the electron affinity value increases, the efficiency gets decreased for all the four different absorber layers” rather than only reporting the results. The same applies to other parameters where sufficient mechanistic view is not provided.

The Response: Authors are thankful to the reviewer for their valuable comment. The revised manuscript provides mechanistic discussion in detail for all the results.

Comment 3: Figure 7: please provide the detailed calculation method to obtain the energy levels of Ec and Ev. How do they compare with those reported in the literature obtained via DFT or XPS/PES?

The Response: The calculation methods and equations to obtain the energy level Ec and Ev have been stated in section 3.6 of the revised manuscript and compared and cited with values obtained by DFT.

 

Reviewer 2 Report

This manuscript reports the comparison of the photovoltaic performance of different absorber materials (CdTe, CIGS, Sb2Se3, and CZTS) with simple structure Au/absorber/CdS/ITO. As the results, the highest 20 efficiency of 28.2 % is achieved for CZTS. The obtained results sound good for preparing solar absorber materials. However, there are some points, which should be clarity.

1. The English should be carefully revised throughout a manuscript
2. The thickness of all layers in a cell should be provided
3. I-V curves should be provided
4. To confirm the change in Jsc value, please provide IPCE measurements

This manuscript can be considered for publication only when the above-mention questions were especially stressed in the revised manuscript. The referee would like to review a revised version of this paper in the future.

Author Response

Here, I am attaching the pointwise responses to the referee’s comments.

REFEREE REPORT(S)

Reviewer # 2

Comment 1 The English should be carefully revised throughout a manuscript

The Response: We have gone through the manuscript carefully, and English-related corrections have been made in the revised manuscript.

Comment 2: The thickness of all layers in a cell should be provided

The Response: The thickness of all the layers is varied to check the overall performance of the device. The optimized thickness for all the absorber layers is taken as 4 µm to achieve the maximum efficiency, as shown in Fig. 2 of the revised manuscript.

Comment 3: I-V curves should be provided

The Response: I-V characteristics curves for all the absorber layers have been provided in Fig. 4(a) of section 3.3 of the revised manuscript.

Comment 3: To confirm the change in Jsc value, please provide IPCE measurements

The Response: For the confirmation of various output parameters, including Jsc, a QE plot for all the absorber layers is presented in Fig. 4(b) of the revised manuscript. 

 

Reviewer 3 Report

The article entitled "Performance and Comparison of Various Thin-Film based Absorber Materials: A viable Approach for Next Generation Solar Cells" presents the photovoltaic performance of different absorber materials including CdTe, CIGS, Sb2Se3, and CZTS with structure of Au/absorber/CdS/ITO. The work done in this article was to optimize the mentioned parameters and their effect on the performance of the solar cell. The article needs to be revised.

• The subtitles of Figures 2, 3, 4 and 6 should be separate for each shape and the shapes should be a, b and c ...
• Increasing the thickness of absorbent layers from 2 µm to 4 µm is also economically justified? It's better to explain.
• It is better to include Poisson's mathematical equations and the continuity mentioned in the text.
• Simulation algorithms are brought with SCAPS. Please give the algorithm and optimization method in details.
• In this article some absorber materials including CdTe, CIGS, Sb2Se3, and CZTS have been studied, and therefore, some recent works have been recommended to consider in Introduction section: 10.1016/j.solener.2021.08.044; 10.1007/s11082-020-02464-9; 10.1038/s41598-020-75686-2; Coatings 2021, 11, 52. https://doi.org/10.3390/coatings11010052.
• The manuscript needs to be carefully edited. For example the title of section 3.5. Energy band Diagram of CZTS/CdS based solar cell should be changed to 3.6.
• Some important factors such as fill factor and EQE should be more explained and addressed by proper equations.
• The main work done in this article was to optimize the mentioned parameters and their effect on the performance of the solar cell, which is not considered as an innovation. The novelty needs to be highlighted.
• The representation of mode field distributions of the proposed structure for various layers of CdTe/CIGS/CZTS/Sb2Se3 are recommended.

 

Author Response

Here, I am attaching the pointwise responses to the referee’s comments.

REFEREE REPORT(S)

Reviewer # 3

Comment 1 The subtitles of Figures 2, 3, 4 and 6 should be separate for each shape and the shapes should be a, b and c.

The Response: Authors are thankful to the reviewer for their valuable suggestion. The subtitles have been added in the figures in the revised manuscript as suggested.

Comment 2: Increasing the thickness of absorbent layers from 2 µm to 4 µm is also economically justified? It's better to explain.

The Response: We agree with the reviewer’s comment. For all the absorber layers, the maximum efficiency is achieved when the optimized thickness is taken as 4 µm. In this work, for 2 µm thickness, efficiency is >1% less than 4µm thickness for CdTe, CIGS and Sb₂Se₃ absorber layers and for CZTS is > 6 %. Thus, for mass production, considering the importance of efficiency, materials cost will not matter much for materials made from cheaper elements (and even for CIGS) as the material cost is much lesser than the processing cost.

Comment 3: It is better to include Poisson's mathematical equations and the continuity mentioned in the text.

The Response: Poisson and continuity equations have been mentioned in the revised manuscript.

Comment 4: Simulation algorithms are brought with SCAPS. Please give the algorithm and optimization method in details

The Response: In the revised manuscript, the algorithm and optimization method has been added.

Comment 5: In this article some absorber materials including CdTe, CIGS, Sb₂Se₃, and CZTS have been studied, and therefore, some recent works have been recommended to consider in Introduction section: 10.1016/j.solener.2021.08.044; 10.1007/s11082-020-02464-9; 10.1038/s41598-020-75686-2; Coatings 2021, 11, 52. https://doi.org/10.3390/coatings11010052.

The Response: The recent works on absorber layers have been added and cited, as suggested, in the revised manuscript.

Comment 6: The manuscript needs to be carefully edited. For example the title of section 3.5. Energy band Diagram of CZTS/CdS based solar cell should be changed to 3.6.

The Response: We have gone through the manuscript carefully and made the required corrections in the revised work.

Comment 7: Some important factors such as fill factor and EQE should be more explained and addressed by proper equations.

The response: With the help of proper equations, fill factor, EQE, and other factors have been explained in the revised manuscript.

Comment 8: The main work done in this article was to optimize the mentioned parameters and their effect on the performance of the solar cell, which is not considered as an innovation. The novelty needs to be highlighted.

The Response: The novelty and the aim behind the work is described in the revised manuscript.

Comment 9: The representation of mode field distributions of the proposed structure for various layers of CdTe/CIGS/CZTS/Sb₂Se₃ are recommended.

The Response: Thank you very much for the comment. It was new to us. At present, we don’t have the resources to carry out these experiments and fittings. We shall indeed look for it and carry out such work in the future.

Reviewer 4 Report

Authors of this work have tried to examine the influence of absorber layer thickness, acceptor density, electron affinity, back contact work function, and temperature on the performance of Au/(CdTe or CIGS or Sb2Se3 or CZTS)/CdS/ITO structure. Among others, it was shown that CZTS performs better than others with 28.2 % efficiency relative to CdTe (20.41 %), CIGS (21.41 %) and Sb2Se3 (25.6 %). Finally, the authors have argued that their finding may serve as a model for designing and fabricating cost-effective, efficient, and stable solar cells.

While this work could be publishable, following revisions are necessary.

 

1-      The entire paper needs to be checked by a native English writer since the ms suffers from significant writing issues. There are numerous grammatical errors, and scientific usages used are inappropriate in many instances, including those feasible in figure captions (viz. Fig. 6).

2-      The modeling section (pgs. 2-3) is poorly presented. Details of various criteria used must be presented. The working principles of the protocols of the SCAPS simulation software used must be delineated.

3-      The data and properties summarized in all the tables should be defined appropriately and consistent with the text presented in the ms. For instance, Eg is not defined in the text, which is provided in Table 1. However, the entire paper used words such as “bandgap” or “band-gap”.

 

Author Response

Here, I am attaching the pointwise responses to the referee’s comments.

REFEREE REPORT(S)

Reviewer # 4

Comment 1 The entire paper needs to be checked by a native English writer since the ms suffers from significant writing issues. There are numerous grammatical errors, and scientific usages used are inappropriate in many instances, including those feasible in figure captions (viz. Fig. 6).

The Response: Authors are thankful to the reviewer for their valuable suggestion. We have gone through the manuscript carefully, and many scientific expressions, figures, and English related corrections have been made in the revised manuscript.

Comment 2: The modeling section (pgs. 2-3) is poorly presented. Details of various criteria used must be presented. The working principles of the protocols of the SCAPS simulation software used must be delineated.

The Response: In the revised manuscript, modelling of the device has been modified where the working principle and other related details of SCAPS software have been stated.

Comment 3: The data and properties summarized in all the tables should be defined appropriately and consistent with the text presented in the ms. For instance, Eg is not defined in the text, which is provided in Table 1. However, the entire paper used words such as “bandgap” or “band-gap”.

The Response: We have gone through the manuscript carefully. The parameters presented in the table and the text have been defined when they appear first time in the manuscript. Also, the word band gap and thin film, etc. have been corrected.

Round 2

Reviewer 2 Report

it is OK now

Reviewer 3 Report

The authors have tried to revise the manuscript and the present form can be accepted for publication in Coatings.

Reviewer 4 Report

Authors of the work have revised their paper based on my comments, and I can see there is an improvement compared to the first version of the paper. I cannot see any other improvement from my side, and hence suggest publication of the work.